The continued spread of the HIV epidemic in the absence of an effective prevention underscores the need to develop ways to interrupt HIV transmission. One attractive strategy is a topical vaginal microbicide. For example, the CAPRISA004 study demonstrated partial protection from sexual transmission of HIV-1 by vaginally applied tenofovir gel (Abdool Karim, Q. et al., Science 329, 1168-1174).
Multiple groups have shown that RNA interference (RNAi) can be harnessed to inhibit HIV infection in vitro (Novina, C. D. et al. Nat Med 8, 681-686 (2002); Capodici, J., et al., J Immunol 169, 5196-5201 (2002); Jacque, J. M., et al. Nature 418, 435-438 (2002); Lee, N. S. et al. Nat Biotechnol 20, 500-505 (2002); Coburn, G. A. & Cullen, B. R. J Virol 76, 9225-9231 (2002)). However, application of RNAi for preventing or inhibiting HIV infection is not simple. One must first overcome the hurdle of in vivo siRNA delivery to the immune cells that HIV infects, namely, principally CD4+ T cells and macrophages, which are resistant to most transfection techniques. For example, the cholesterol-conjugated siRNAs that protect against lethal HSV-2 infection in mice (Wu, Y. et al. Cell Host Microbe 5, 84-94 (2009)), although efficiently taken up by epithelial cells throughout the genital tract, including deep in the lamina propria, do not knockdown gene expression in T lymphocytes or macrophages when applied intravaginally to mice.
Peer, D., et al. (Proc Natl Acad Sci USA 104, 4095-4100 (2007)) describes a method for cell-specific siRNA transfection of immune cells that uses a fusion protein composed of a cell-targeting antibody fragment joined to a protamine peptide that binds nucleic acids (Peer, D., et al. Proc Natl Acad Sci USA 104, 4095-4100 (2007)). siRNAs mixed with the fusion protein are taken up by and knockdown gene expression in cells bearing the cognate surface receptor, both in vitro and in tissues following intravenous injection. Modifications of this approach inhibit HIV infection in humanized mice (Kumar, P. et al. Cell 134, 577-586 (2008)). However, antibody-based fusion proteins are very expensive to manufacture, potentially immunogenic and typically require refrigerated storage, making them ill-suited for use in a microbicide for resource-poor settings (Scolnik, P. A. MAbs 1, 179-184 (2009)).
Accordingly, there is a need in the art for compositions and methods for cell-specific siRNA transfection of immune cells.